High nutrient supply and carbohydrate content reduce endophyte and alkaloid concentration

Two controlled environment experiments were performed to test the effects of nitrogen, phosphorus and carbohydrates on endophyte (Neotyphodium lolii) and alkaloid concentrations in ryegrass (Lolium perenne). Three perennial ryegrass cultivars ('high sugar grasses' AberDove and AberDart; control Fennema) that differ in carbohydrate content were infected with three strains of N. lolii (common strain, CS; AR1; AR37). Infected and uninfected plants were grown under high (9 mM) and low (2.25 mM) nitrogen (AberDove, Fennema; CS, AR1, AR37) or under high (2 mM KH2PO4) and low (0.05 mM KH2PO4) phosphorus (AberDart, Fennema; CS, AR1). Quantitative realtime Polymerase Chain Reaction (qPCR) was used to estimate endophyte concentrations in harvested leaf tissues. High N and P supply as well as high carbohydrate content of the host grass reduced endophyte concentrations. Alkaloid production was also reduced under both increased N supply and in the high sugar cultivar, and was linearly related to endophyte concentration (except ergovaline). The results stress the need for wider quantification of fungal endophytes in the grassland/ foliar endophyte context, and have implications for how introducing new cultivars, novel endophytes, or increasing nutrient inputs, affect the role of endophytes in grassland ecosystems. Keywords: Neotyphodium lolii, foliar endophyte, Lolium perenne, perennial ryegrass, qPCR, high sugar ryegrass, nitrogen, phosphate, carbohydrate, AR1, AR37, alkaloids